Often in signal processing applications, particularly modulation and demodulation, orthogonal signals are required to transport and recover latent information relating to some complex passband waveform. Typically, analog techniques are used in RF modulators and demodulators to synthesize a 90° phase shift in a carrier or signal waveform to enable this processing. Passive and active components are used to generate delays at passband corresponding to phase shift at a frequency of interest. These techniques possess certain inaccuracies and implementation tradeoffs. For instance, polyphase filter network approaches require multiple refinement stages to obtain reasonable accuracy while R-C splitters depend on minimizing parasitic elements of the interface amplifiers. Quasi-digital approaches are also used for some applications but trade-off frequency plan, frequency response and power vs. performance.
What are needed are improved methods and systems for generating orthogonal signals for quadrature signal generation.